Methods and Systems for Strengthening LCD Modules

ABSTRACT

Systems and methods for improving strength of thin displays, such as Liquid Crystal Display (LCD) displays, are disclosed. In one embodiment, a display can use an asymmetrical arrangement of layers (e.g., glass layers) where one layer is thicker than another layer. Different scribing techniques can also be used in singulating the different layers. The asymmetrical arrangement and/or scribing techniques can facilitate displays that are not only thin but also adequately strong to limit susceptibility to damage.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/956,312, filed Aug. 16, 2007, entitled “METHODS AND SYSTEMS FORSTRENGTHENING LCD MODULES”, which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

Conventionally, small form factor devices, such as handheld electronicdevices, have a display arrangement that includes various layers. Thevarious layers include at least a display technology layer, and mayadditionally include a sensing arrangement and/or a cover windowdisposed over the display technology layer. In some cases, the layersmay be stacked and adjacent one another, and may even be laminatedthereby forming a single unit. In other cases, at least some of thelayers are spatially separated and not directly adjacent. For example,the cover window and/or sensing arrangement may be disposed above thedisplay such that there is a gap therebetween. By way of example, thedisplay technology layer may include or pertain to a Liquid CrystalDisplay (LCD) that includes a Liquid Crystal Module (LCM). The LCMgenerally includes an upper glass sheet and a lower glass sheet thatsandwich a liquid crystal layer therebetween. The sensing arrangementmay be a touch sensing arrangement such as those used to create a touchscreen. For example, a capacitive sensing touch screen can includesubstantially transparent sensing points or nodes dispersed about asheet of glass (or plastic). In addition, the cover window, which istypically designed as the outer protective barrier, may be glass orplastic. However, glass tends to provide a better protective barriergiven its strength and scratch resistance.

Typically, the LCM is the weakest portion of the display region in termsof strength against bending and damage if dropped. The other layers maybe formed with stronger glass materials and/or may be thicker, therebyincreasing their strength. Because the LCM is the weakest portion, theLCM is often the part of the display region most susceptible to damagewhen the small form factor device is stressed as for example in a dropevent. Here, one or both sheets of glass may crack or break as a resultof the drop event. This problem is exacerbated by the trend to makehandheld electronic devices thinner.

Thus, there is a need for improved approaches to make displays that arenot only thin but also sufficiently strong to avoid unnecessary damage.

SUMMARY OF THE INVENTION

The invention is related to systems and methods for improving strengthof thin displays, such as Liquid Crystal Display (LCD) displays. In oneembodiment, a display can use an asymmetrical arrangement of layers(e.g., glass layers) where one layer is thicker than another layer.Different scribing techniques can also be used in singulating thedifferent layers. The asymmetrical arrangement and/or scribingtechniques can facilitate displays that are not only thin but alsoadequately strong to limit susceptibility to damage.

The systems and methods are especially suitable for displays (e.g., LCDdisplays) assembled in small form factor electronic devices such ashandheld electronic devices (e.g., cell phones, media players, PDAs,remote controls, etc.). The systems and methods can be used for displaysfor portable electronic devices (e.g., portable computers, tabletcomputers, displays, monitors, televisions, etc.).

The invention can be implemented in numerous ways, including as amethod, system, device, or apparatus. Several embodiments of theinvention are discussed below.

As a display for an electronic device, where the display has anasymmetric glass configuration, one embodiment of the invention includesat least: a first glass sheet having a first thickness and having afirst edge character; and a second glass sheet proximate but spacedapart from the first glass sheet, the second glass sheet having a secondthickness, where the second thickness is different than the firstthickness. The second glass sheet having a second edge character, andthe second edge character being different than the first edge character.

As a method of forming a display with an asymmetric glass configuration,one embodiment of the invention includes at least: providing a firstglass sheet having a first thickness; providing a second glass sheethaving a second thickness; cutting the first glass sheet with a firstcutting process, the first cutting process forming a first edge on thefirst glass sheet; cutting the second glass sheet with a second cuttingprocess that is different than first cutting process, the second cuttingprocess forming a second edge on the second glass sheet; and positioningthe first and second sheets relative to one another in order to form thedisplay.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements, and in which:

FIG. 1A is simplified diagram of an electronic device, in accordancewith one embodiment of the present invention.

FIG. 1B is simplified diagram of an electronic device, in accordancewith one embodiment of the present invention.

FIG. 2 is a diagram of a Liquid Crystal Module (LCM), in accordance withone embodiment of the present invention.

FIG. 3 is a side by side comparison of asymmetrical glass configurationand a symmetrical glass configuration, in accordance with one embodimentof the present invention.

FIG. 4 is a method of producing a LCM, in accordance with one embodimentof the present invention.

FIG. 5 is a method of producing a LCM, in accordance with anotherembodiment of the present invention.

FIG. 6 is a diagram of a mother sheet containing a plurality of LCMs, inaccordance with one embodiment of the present invention.

FIG. 7A is a diagram of a laser scribing process, in accordance with oneembodiment of the present invention.

FIG. 7B is a side elevation view in cross section of a piece of glassafter a laser scribing process, in accordance with one embodiment of thepresent invention.

FIG. 8A is a diagram of a conventional wheel cutting process.

FIG. 8B is a side elevation view in cross section of a piece of glassafter a wheel cutting process.

DETAILED DESCRIPTION OF THE INVENTION

The invention is related to systems and methods for improving strengthof thin displays, such as Liquid Crystal Display (LCD) displays. In oneembodiment, a display can use an asymmetrical arrangement of layers(e.g., glass layers) where one layer is thicker than another layer.Different scribing techniques can also be used in singulating thedifferent layers. The asymmetrical arrangement and/or scribingtechniques can facilitate displays that are not only thin but alsoadequately strong to limit susceptibility to damage.

The systems and methods are especially suitable for displays (e.g., LCDdisplays) assembled in small form factor electronic devices such ashandheld electronic devices (e.g., cell phones, media players, PDAs,remote controls, etc.). The systems and methods can be used for displaysfor portable electronic devices (e.g., portable computers, tabletcomputers, monitors, displays, televisions, etc.).

Small form factor devices such as handheld electronic devices typicallyinclude a display region that includes various layers. The variouslayers may include at least a display, and may additionally include asensing arrangement and/or a cover window disposed over the display. Insome cases, the layers may be stacked and adjacent one another, and mayeven be laminated thereby forming a single unit. In other cases, atleast some of the layers are spatially separated and not directlyadjacent. For example, the cover window and/or sensing arrangement maybe disposed above the display such that there is a gap therebetween. Byway of example, the display may include a Liquid Crystal Display (LCD)that includes a Liquid Crystal Module (LCM). The LCM generally includesat least an upper glass sheet and a lower glass sheet that sandwich aliquid crystal layer therebetween. The sensing arrangement may be atouch sensing arrangement such as those used to create a touch screen.For example, a capacitive sensing touch screens can includesubstantially transparent sensing points or nodes dispersed about asheet of glass (or plastic). In addition, the cover window, which istypically designed as the outer protective barrier, may be glass orplastic. However, glass tends to provide a better protective barriergiven its strength and scratch resistance.

Often, the LCM is the weak link in the display region in terms ofstrength against bending and damage if dropped. The other layers may beformed with stronger glass materials and further they may be thickerthereby increasing their strength. Because it is the weakest portion,the LCM is often the part of the display region most susceptible todamage when the small form factor device is stressed as for example in adrop event. By way of example, one or both sheets of glass may crack orbreak. This problem is exacerbated with ever thinning electronicdevices, i.e., there is a continuing need to make things smaller andtherefore thinner (and thinner typically lends itself to less strength).Conventionally, a LCM includes a symmetric glass configuration where theupper and lower glass sheets have the same thickness of about 0.4 mm orgreater. Recently, there has been a push to move the symmetricalthickness to glass layers of about 0.3 mm (although only a few caseshave been implemented), and it is generally believed that the industryat some point may move to a symmetrical thickness to glass layers ofabout 0.225 mm.

Asymmetrical glass sheet thickness has been proposed as one means ofimproving strength of LCMs. This works by having LCM depend on thethicker of the two sheets for most of its strength. For the same overallstack height, an assembly having one sheet at 0.35 and the other sheetat 0.25 mm has an overall higher bending strength than an assembly oftwo sheets at 0.3 mm each. This is because the bending strength goes asthe square of the thickness, meaning that small increase in thicknesscan have a relatively large effect on strength.

Utilizing laser scribing in favor of conventional mechanical wheelscribing has also been proposed as one means of improving strength ofLCMs. Laser scribing may provide a 2× to 3× strength improvement overother methods of glass cutting especially mechanical methods such aswheel scribing.

Unfortunately, laser scribing has its limitations. Laser scribing is notcapable of cutting glass sheets of very small thickness. A sufficientlylarge thickness is typically needed to prevent the generated thermalgradient from penetrating all the way through to the opposite side ofthe glass, thereby diminishing the thermally generated tensile stressneeded to separate the glass. By way of example, problems may arise whentrying to apply laser scribing to glass thicknesses less than 0.25 mmand even more particularly less than 0.225 mm in that the thermalgradient necessary for successful scribing is difficult to properlygenerate and control in such thin glass sheets. This means that thecurrent state of the art may not allow for two sheets of less than 0.25mm to be laser scribed with sufficiently high yields. Therefore, it isgenerally believed that as the industry pushes towards thinner sheets,laser scribing will become increasingly challenging unless newtechnologies are developed to overcome its deficiencies.

The present invention overcomes the current limitations of laserscribing by utilizing an asymmetrical glass configuration and laserscribing the thicker glass sheet where the thicker glass sheet is formedto a dimension capable of being laser scribed. That is, the thickerglass sheet is configured to be as thick as necessary to perform laserscribing thereon (able to form desired thermal gradients). In oneembodiment, the thickness is greater than 0.225 mm, more particularlygreater than 0.25 mm, even more particularly greater than 0.275 mm andyet more particularly greater than 0.3 mm. Not only does the thickerglass sheet provide most of its structural rigidity to the assembly dueto its thickness but now also to its stronger laser scribed edges (a 2×to 3× strength improvement of laser scribing can be obtained on the edgethat matters). Since the thinner glass sheet provides little strength tothe assembly anyway, and because it may be too thin for laser scribing,it can be cut with normal wheel scribing providing reasonably high yieldrates for both sides.

In order to maintain the same dimensional envelope as the industry, inone example, for what would typically be a 0.225/0.225 mm envelope, theLCM according to one embodiment of the invention can be configured withabout a 0.275 mm glass sheet having laser scribed edges and a 0.175 mmglass sheet having edges scribed with something other than laserscribing (e.g., mechanical wheel scribing). Of course, other dimensionsand other envelopes can be used. For example, according to anotherembodiment, the LCM can be configured with about a 0.25 mm glass sheethaving laser scribed edges and a 0.15 mm glass sheet having edgesscribed with something other than laser scribing.

These and other embodiments of the invention are discussed below withreference to FIGS. 1-8B. However, those skilled in the art will readilyappreciate that the detailed description given herein with respect tothese figures is for explanatory purposes as the invention extendsbeyond these limited embodiments.

FIGS. 1A and 1B are simplified diagrams of an electronic device 10A and10B, in accordance with one embodiment of the present invention. Theelectronic devices 10A and 10B may for example be embodied as portableor handheld electronic devices having a thin form factor. The electronicdevices 10A and 10B may for example correspond to media players, mediastorage devices, PDAs, tablet PCs, computers, cellular phones, smartphones, GPS units, remote controls, and the like. By way of example, theelectronic device may correspond to an iPhone™ or iPod™ manufactured byApple Inc. of Cupertino, Calif.

Both electronic devices 10A and 10B include a display area 12 that isdisposed within a housing 14 of the electronic devices 10A and 10B. Theelectronic device 10A of FIG. 1A includes a full view or substantiallyfull view display area 12 that consumes a majority if not all of thefront surface of the electronic device 10A. The electronic device 10B ofFIG. 1B includes a partial display area 12 that only takes up a portionof the front surface of the electronic device 10B. The display area 12may be embodied in a variety of ways. In one example, the display area12 consists of at least a display such as a flat panel display and moreparticularly an LCD display. The display area 12 may additionallyinclude a cover window that is positioned over a display. The coverwindow may be formed from glass. As should be appreciated glass resistsscratching and therefore typically provides a better surface thanplastic especially for portable electronic devices that are placed inbags, cases, backpacks, pockets, and the like. The display area 12 mayalternatively or additionally include a touch sensing device positionedover the display. For example, the display area 12 may include one ormore glass layers having capacitive sensing points distributed thereon.Each of these components can be separate layers or they may beintegrated into one or more stacks. In some cases, the cover window actsas the outer most layer of the display area and the display acts as theinner most layer of the display area.

FIG. 2 is a diagram of an LCM 100, in accordance with one embodiment ofthe present invention. The LCM 100 may for example be included in thedisplay region described in FIGS. 1A and 1B.

The LCM 100 includes a lower glass sheet 102 and an upper glass sheet104 that are attached together via a perimeter seal 106. Thisarrangement is configured to encapsulate a liquid crystal layer 108internally therein. In most cases, the upper glass sheet 104 includes acolor filter 110 and the lower glass sheet includes drive electronics112 such as Thin Film Transistor (TFT) in order to create colored pixelsof a display. Although not shown, a polarizer may be additionally placedover the upper glass sheet 104 and a diffuser for illumination may beplaced behind the lower glass sheet 102.

In accordance with one embodiment of the present invention, the LCM 100includes an asymmetric glass configuration such that the upper and lowerglass sheets 102 and 104 have different thicknesses t1 and t2. That is,one is configured to be thicker while the other is configured to bethinner. Put another way, one glass sheet has a thickness greater thanthe thickness of the other glass sheet, or one glass sheet has athickness less than the thickness of the other glass sheet. In oneembodiment, the upper glass sheet 104 is configured with a largerthickness than the lower glass sheet 102. In another embodiment, thelower glass sheet 102 is configured with a larger thickness than theupper glass sheet 104.

Furthermore, the thicker glass sheet includes a first edge 114A, and thethinner glass sheet includes a second edge 114B that is different thanthe first edge 114A. The first edge 114A may for example have a fine cutedge and the second edge 114B may have a coarse cut edge. The first edge114A may be configured with less stress concentrations or substantiallyno microcracks than the second edge 114B thereby increasing the strengthof the thicker glass sheet. The first edge 114A may be configured to besharper than the second edge 114B thereby increasing the strength of thethicker glass sheet.

The first edge 114A may be formed via a first process and the secondedge 114B may be formed via a second process that is different than thefirst process. The first process may for example be a process thatlimits stress concentrations and produces a clean sharp edge (e.g., flatand of regular geometric form, uniform and without defects, with “waterclear” surface quality). Since this typically cannot be accomplishedwith mechanical processes, the first process may be a process other thana mechanical process (e.g., wheel scribing). In one embodiment, thefirst edge 114A is created via a laser scribing process. In fact, thethickness of the thicker layer that includes the first edge 114A may bespecifically configured for a laser scribing process. For example, thethickness may be configured as at least the lowest possible thicknesscapable of being laser scribed. In one embodiment, the second edge 114Bis created via a mechanical wheel scribing process capable of cuttingglass of almost any thickness. In fact, the thickness of the thinnerlayer including the second edge 114B may be configured less than thelowest possible thickness capable of being laser scribed.

The materials used to form the glass sheets may be widely varied. Inmost cases, the glass sheets are formed from the same glass material.However in some cases, additional strength benefits may be realized whenusing different materials. For example, the thicker glass sheet may beformed from a stronger glass material than the thinner glass sheet (orvice versa). The material typically needs to be selected based on theability to properly encapsulate the liquid crystal layer. The materialstypically need to be sodium free for this reason. The glass may bemineral glass. Examples of glass materials include alimino silicate(e.g., DVTS from Corning), sodalime, borosilicate, and the like. In oneparticular implementation, the glass sheets are formed from the samematerial, and further using borosilicate. Borosilicate is typical andmay be preferred for TFT LCDs. Further, older STN type LCD displays canuse sodalime, but typically not the newer TFT type, due to corrosionthat may be caused by the sodium in the sodalime glass.

The materials may be chemically strengthened (both or one). However, itshould be noted that glass for TFT LCD displays is typically notchemically strengthened for several reasons: (1) flatness problemsinduced by chemical strengthening resulting in optical issues, and (2)need for sodium in the glass for chemical strengthening, which willcorrode conductive traces unless the glass is passivated by an extralayer of material between the conductive film(s) and the glass.

The sizes of the glass sheets may be widely varied. In one embodiment,the combined thickness of the upper and lower sheets in the asymmetricalglass configuration are configured to equal the combined thickness ofthe typical symmetrical glass configuration. For example, if thestandard symmetrical glass configuration is typically 0.3 mm/0.3 mm,then the asymmetrical glass configuration's total thickness is about 0.6mm and if the symmetrical glass configuration is typically 0.225/0.225mm then the asymmetrical glass configuration is about 0.45 mm (thesetotal thicknesses include the glass sheets, they do not include theliquid crystal layer between the two sheets of glass nor other layersabove and below the glass sheets in the final assembly). In oneembodiment, in cases such as these, the amount of thickness added to thethicker sheet of glass is typically subtracted from the thinner sheet ofglass (e.g., increased and decreased the same amount-follow 1:1 ratio).By way of example, the % change of increase/decrease for each sheet maybe between about 25%-1%, more particularly between about 25% to about10%, even more particularly 25% to about 20%, and even more particularly23% to about 22%. For example, an increase and decrease of 0.05 mm to asymmetrical configuration of 0.225/0.225 can create an asymmetricalconfiguration 0.275/0.175 which is about a 22.2% change from thesymmetrical dimensions.

Several examples of asymmetrical glass configuration using a 1:1 ratioand a 0.45 mm combined thickness are as follows: 0.3/0.15 mm,0.295/0.155 mm, 0.29/0.16 mm, 0.285/0.165 mm, 0.28/0.17 mm, 0.275/0.175mm, 0.27/0.18 mm, 0.265/0.185 mm, 0.26/0.19 mm, 0.255/0.195 mm, or0.25/0.20 mm. These have been rounded to nearest 10^(th), 100^(th) or1000^(th), and therefore may vary slightly in actual production. Ofcourse, these configurations are exemplary and not necessarylimitations. For example, other envelopes besides a 0.45 combinedthickness may be used. The same, similar or different increments may beapplied.

In another embodiment, the combined thickness of the upper and lowersheets in their asymmetrical glass configuration do not follow the sameoverall thickness of a standard symmetrical glass configuration. Incases such as these, the asymmetrical glass configuration is not boundto the same increases and decreases. That is, various ratios ofincreased thickness and decreased thickness can be used. The ratio ofincrease to decrease does not need to be 1:1. By way of example, theratio may be configured to decrease the thickness of the thinner sidemore than the increase to the thickness of the thicker side or viceversa depending on the needs of the system. In some cases, only one sideis changed. For example, an increase to the thicker side with no changeto other side (or vice versa).

In one particular embodiment, for a symmetric configuration of about0.225/0.225 mm or a combined thickness of about 0.45, an asymmetricalglass configuration of about 0.275/0.175 mm (an increase and decrease inthickness of about 0.05 mm) can be used. Of course, other embodimentsare not limited to such a combined thickness or such amounts ofincrease/decrease in thickness of the two sheets. For example, thethickness of the thicker sheet may be increased/decreased as much as 40%of its centerline value (0.225/0.225) to as little as 1% of itscenterline value.

One potential problem with decreasing size of thinner sheet is that thethinner sheet loses rigidity and becomes more flexible. As a result, itbecomes increasing difficult to maintain a consistent gap between upperand lower glass sheets (which can result in adverse optical effects).Therefore, in one embodiment, high density spacer elements may be placedbetween the glass sheets to keep the gap consistent. By way of example,spacer elements may be provided every 6-10 pixels. For example 2 rows, 5pixels wide. The spacers can be placed across entire surface at the 4corners of the desired matrix. Although rare, conventional spacers maybe placed at about every 50-80 pixels.

As noted above, the electronic device can be a handheld electronicdevice or a portable electronic device. The invention services to enablea display to be not only thin but also adequately strong. Since handheldelectronic devices and portable electronic devices are mobile, they arepotentially subjected to various different impact events and stressesthat stationary devices are not subjected to. As such, the invention iswell suited for implementation of displays for handheld electronicdevice or a portable electronic device that are designed to be thin.

In one embodiment, the size of the display depends on the size of theassociated electronic device. For example, with handheld electronicdevices, the display (screen) is often not more than five (5) inchesdiagonal. As another example, for portable electronic devices, such assmaller portable computers or tablet computers, the display (screen) isoften between four (4) to twelve (12) inches diagonal. As still anotherexample, for portable electronic devices, such as full size portablecomputers, displays or monitors, the display (screen) is often betweenten (10) to twenty (20) inches diagonal or even larger. However, itshould be appreciated that with larger the screen sizes, the thicknessof the glass layers may need to be greater. The thickness of the glasslayers may need to be increased to maintain planarity of the largerglass layers. While the displays can still remain relatively thin, theminimum thickness can increase with increasing screen size. For example,the minimum combined thickness of the layers (sheets) t1 and t2 shown inFIG. 2 can correspond to about 0.4 mm for small handheld electronicdevices, about 0.6 mm for smaller portable computers or tabletcomputers, about 1.0 mm or more for full size portable computers,displays or monitors, again depending on the size of the screen.

Although not shown in FIG. 2, other layers may be disposed over the LCM.The layers may for example include laminated layers or spatiallyseparated layers. The layers may for example be selected from sensinglayers, and cover windows, and the like.

FIG. 3 is a side by side comparison of asymmetrical glass configuration150 and a symmetrical glass configuration 152, in accordance with oneembodiment of the present invention. As shown, both include an upperglass sheet 154 and a lower glass sheet 156 that sandwich a liquidcrystal layer 158 therebetween. The upper glass sheet 154 can be ColorFilter (CF), and the lower glass sheet 156 can be Thin Film Transistor(TFT) glass. The liquid crystal layer 158 is also surrounded at theperiphery of the LCMs via a gasket or seal 160. In the symmetrical glassconfiguration 152, the upper and lower glass sheets 154 and 156 have thesame thickness. For example, the upper CF glass can have the samethickness as the lower TFT glass. In the asymmetrical glassconfiguration 150, the upper and lower glass sheets 154 and 156 havedifferent thicknesses. For example, the upper CF glass is thinner andthe lower TFT glass is thicker. Furthermore, in the symmetrical glassconfiguration 150, the cut edges 162 of both the upper and lower glasssheets 154 and 156 are formed from the same process, a process notconfigured to enhance strength but rather limit strength (not laserscribing). By way of example, both sheets are cut via a mechanicalscribing process such as wheel scribing. Furthermore, in one embodimentthe asymmetrical glass configuration 150, the cut edges 160 of both theupper and lower glass sheets 154 and 156 are formed from differentprocesses, one of which is configured to enhance strength. By way ofexample, the thicker sheet may be cut via a laser scribing process whilethe thinner sheet may be cut via a mechanical scribing process (e.g.,wheel scribe).

FIG. 4 is a method 200 of producing an LCM, in accordance with oneembodiment of the present invention. The method 200 may for example beused to create any of the LCMs disclosed herein. The method 200 mayinclude block 202 where an asymmetrical glass configuration is providedfor small form factor devices (e.g., thin). That is, an LCM thatincludes an upper and lower glass sheet of differing thicknesses isprovided. In one embodiment, the upper sheet is thicker while the lowersheet is thinner. In another embodiment, the lower sheet is thickerwhile the upper sheet is thinner. In one particular embodiment, theupper glass carrying a CF layer is thinner while the lower glasscarrying a TFT layer is thicker.

The combined thickness for the two sheets for LCMs used in small formfactor devices may be widely varied. The current trend is that thecombined thickness is ever shrinking in order to accommodate thinner andthinner devices or devices that need additional space for addedfunctionality. By way of example, the combined thickness of the twosheets may be less than or equal to 0.8 mm, more particularly less thanor equal to 0.6 mm, even more particularly less than or equal to 0.5 mm,even more particularly, less than or equal to 0.45 mm, and yet even moreparticularly less than or equal to 0.4 mm.

In one embodiment, the asymmetry is caused by equal but opposite changesin thickness to the glass sheets. For example, the thickness isincreased by the same amount the thickness of the other glass sheet isdecreased. The % change from the centerline thickness can be widelyvaried. It may be as great as 40% from the centerline value to as littleas 1% of the centerline value. In some cases, it is between 33% andabout 10%, while in other cases, it is between about 25% and about 20%.Furthermore, it may be more specifically between about 23% and about22%, and more particularly around 22.2%. By way of example, if thecenterline value is 0.225 then a 22.2% change would result in anasymmetrical glass configuration of about 0.275/0.175 or an increase ofabout 0.05 mm and a decrease of about 0.05 mm. It should be appreciatedthat these examples are given by way of example and not by way oflimitation.

In another embodiment, the asymmetry is caused by different and oppositechanges in the thickness of the glass sheets. For example, the thicknessof one glass sheet may be increased more than a decrease of the otherglass sheet (or vice versa). Furthermore, only one of the thicknessesmay be altered in order to create the asymmetry. For example, one mayremain unchanged while the other is increased or decreased. By way ofexample, one may be increased as much as 40% from centerline value whilethe other remains unchanged or changed a different percentage (%) fromcenterline value. In some examples, the thickness of each sheet can varybetween about 33% and about 10%, while in other cases, it varies betweenabout 25% and about 20%. Furthermore, it may be more specifically varybetween about 23% and about 22%. For example, any ratio between40-0%/40-0% of centerline value may be used so long as they aredifferent. In some cases they are substantially different (greater than5% difference, e.g., 20%/14%) while in other cases they aresubstantially close in the % changed (less than 5% difference, e.g.,20%/16%). Of coarse they may even be greater than 10% difference or lessthan 1% difference. The difference generally depends on the desiredneeds of the system.

The method 200 also may also include block 204 where the thicker glasssheet is singulated via a first process. The first process is configuredto reduce microcracks and/or stress concentrations at the edges of thethicker sheet thereby increasing its overall strength.

The method 200 can also include block 206 where the thinner glass sheetis singulated via a second process that is different than the firstprocess. Because the LCM strength is relying on the strength of thethicker sheet, the same attention given to the edge of the thicker sheetdoes not have to be made to the thinner sheet (i.e., the thicker sheetis providing most of the strength to the LCM). However, in analternative embodiment, the edge of the thinner glass can also use thefirst process.

In most cases, the thickness of each sheet is configured for itsparticular process in order to obtain the desired cut with high yieldrates. That is, the thickness is selected based on the capabilities ofthe process being used. In one embodiment, the thicker glass sheet issingulated using a laser scribe process, and the thinner glass sheet,which may be incapable of being laser scribed because of its thinness,is singulated with a process other than laser scribing. By way ofexample, conventional mechanical scribing techniques may be used tosingulate the thinner glass sheet. For example, a mechanical cuttingwheel may be used. In one embodiment, the thickness of the thicker sheetis greater than or equal to the minimum thickness required for the firstprocess. As should be appreciated, the limit on how thin the glass canbe for laser scribing can be based on the depth of the thermal gradientnecessary for producing the required tensile stress in the glass. As theglass gets much thinner (e.g., less than 0.25-0.3 mm), the thermalgradient penetrates all the way through the backside of the glass andcan disrupt its ability to create sufficient stress for crackpropagation. Since there is a gap between the two sheets for the liquidcrystal region, there would not be enough thermal conduction betweenthem to change the minimum thickness limitation.

In one embodiment, the minimum thickness is a thickness greater thanabout 0.225. In another embodiment, the minimum thickness is a thicknessgreater than about 0.23. In another embodiment, the minimum thickness isa thickness greater than about 0.235. In another embodiment, the minimumthickness is a thickness greater than about 0.24. In another embodiment,the minimum thickness is a thickness greater than about 0.245. Inanother embodiment, the minimum thickness is a thickness greater thanabout 0.25. In another embodiment, the minimum thickness is a thicknessgreater than about 0.255. In another embodiment, the minimum thicknessis a thickness greater than about 0.26. In another embodiment, theminimum thickness is a thickness greater than about 0.265. In anotherembodiment, the minimum thickness is a thickness greater than about0.27. In another embodiment, the minimum thickness is a thicknessgreater than about 0.275. In another embodiment, the minimum thicknessis a thickness greater than about 0.28. In another embodiment, theminimum thickness is a thickness greater than about 0.285. In anotherembodiment, the minimum thickness is a thickness greater than about0.29. In another embodiment, the minimum thickness is a thicknessgreater than about 0.295. In another embodiment, the minimum thicknessis a thickness greater than about 0.3.

FIG. 5 is a method 300 of producing an LCM, in accordance with oneembodiment of the present invention. The method 300 may for example beused to create any of the LCMs disclosed herein. The method can includeblock 302 where an LCM stack having an asymmetrical glass thicknessbetween upper and lower glass sheets is formed. The method can alsoinclude block 304 where the thinner glass sheet is cut via a mechanicalscribing process such as mechanical wheel scribing. The method can alsoinclude block 306 where the thicker glass sheet is cut via laserscribing process. In laser scribing, the thickness of the thicker glasssheet is typically configured for laser scribing, i.e., it has theminimum thickness necessary to create the proper thermal gradient.

The cutting operations can be performed at different times orsimultaneously. Further, the cutting operations may be performed in thesame machine at the same location or different locations, or in entirelydifferent machines.

FIG. 6 is a diagram of a mother sheet 400 containing a plurality of LCMs402, in accordance with one embodiment of the present invention. Themother sheet 400 includes upper and lower sheets 404 and 406 having anasymmetrical configuration. The sheets 404 and 406 are separated by agasket 408 interposed between them. In most cases, the seal doesn'tprovide a lot of structural rigidity to the LCMs as it is formed from arelatively compliant material. The gasket 408 helps seal the liquidcrystal material between the two glass sheets 404 and 406. The gasket408 defines each of the LCMs 402 carried by the mother sheet 400. In oneembodiment, during a singulation procedure to separate individual LCMs402 from the mother sheet 400, the thicker glass sheet 406 is cut via alaser scribing process, and the thinner glass sheet 404 is cut via amechanical scribing process. The scribing order may be widely varied. Insome cases, the thinner side is singulated first, then the thicker side,and in other cases, the thicker side is first and then the thinner side.The separation may be accomplished in one or more cutting operations. Inone embodiment, a first cutting process is used to scribe bars having arow of LCMs from the mother sheet, and a second cutting process is usedto cut individual LCM cells from the bars. The first cutting operationmay include for example scribing the thinner side, rotating the motherglass and then scribing the thicker side. The second cutting process mayfollow a similar sequence. Of course other cutting operations may beused.

FIG. 7A is a diagram of a laser scribing process 500, and FIG. 7B is aside elevation view in cross section of a piece of glass 502 after alaser scribing process. As shown in FIG. 7A, a laser 504 is madeincident on the surface of the glass 502 and moved in a lineardirection. Furthermore, a cooling beam 506 is applied to the surface ofthe glass 502 behind the laser 504. Both beams move across the glasssurface in alignment one after the other, having started at an initialcrack on the edge of the glass which is created via an alternate processsuch as a mechanical scribe process. Because the thermal gradientcreated by the rapid heating (laser) and cooling (cooling nozzle) merelygenerates enough tensile stress to overcome the glass material'sinternal strength and thusly propagate the initial crack, no material isremoved in the process of laser scribing, but rather a shallowseparation of the glass is achieved along the scribe line. The laserscribe line may for example be about 50-100 microns deep. Generallyspeaking, the laser rapidly heats the glass (substantially all of theenergy is absorbed at the surface due to wavelength of laser, which istypically a CO2 type laser) and a mist of de-ionized water and air, orethanol and nitrogen (cooling medium) subsequently rapidly cools it tocreate a thermal gradient about the line. The thermal gradient providesa stress that propagates the initial crack at the edge across thesurface thereby scribing the sheet. As shown in FIG. 7B, after the beamshave passed and after a break force has been applied to sever the glass502 along the line, a clean surface 512 is created. The surface 512 is agenerally free of micro-cracks and micro-chips, and includes very sharpupper and lower edges 514.

FIG. 8A is a diagram of a conventional wheel cutting process 520, andFIG. 8B is a side elevation view in cross section of a piece of glass522 after a wheel cutting process. As shown in FIG. 8A. a rotatingcutting wheel (e.g., blade) 524 is moved linearly across the surface ofthe glass 522 in order to create a cutting line 526. The wheel 524typically does not cut completely through the glass 522 but ratherscribes the surface of the glass 522 to some depth that can be asshallow as only a few tens of microns or as high as hundreds of microns,and sometimes all the way through the glass for sheets of smallthickness. Depth of scribe depends on the configuration of the wheel,scribe pressure, and scribing rate. Optimal depth of scribe depends onglass thickness, composition, particular end-use application, and otherfactors. As the cutting wheel 524 encounters glass material, itabrasively attacks the glass thereby creating micro-cracks andmicro-chips from a series of small explosions as the compressive stressof the material is overcome by the scribe pressure. As shown in FIG. 8B,after the wheel has passed and after a force has been applied to severthe glass along the line, a surface 528 with micro-cracks andmicro-chips 530 is created. The micro-cracks and micro-chips 530 weakenthe glass sheet 522 and make it more susceptible to breaking ordeveloping larger cracks.

The various aspects, features, embodiments or implementations of theinvention described above can be used alone or in various combinations.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of the disclosure or of what maybe claimed, but rather as descriptions of features specific toparticular embodiment of the disclosure. Certain features that aredescribed in the context of separate embodiments can also be implementedin combination. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations, one or more features from a claimed combination can insome cases be excised from the combination, and the claimed combinationmay be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, and equivalents, whichfall within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andapparatuses of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents as fall within the truespirit and scope of the present invention.

1. A display for an electronic device, said display having an asymmetricglass configuration, said display comprising: a first glass sheet havinga first thickness and having a first edge character; and a second glasssheet proximate but spaced apart from the first glass sheet, the secondglass sheet having a second thickness, the second thickness beingdifferent than the first thickness, and the second glass sheet having asecond edge character, the second edge character being different thanthe first edge character.
 2. The display as recited in claim 1, whereinthe first edge character is a fine cut edge and the second edgecharacter is a coarse cut edge.
 3. The display as recited in claim 1,wherein the first edge character has less stress concentrations than thesecond edge character.
 4. The display as recited in claim 1, wherein thefirst edge character is sharper than the second edge character.
 5. Thedisplay as recited in claim 1, wherein the glass sheets are formed fromborosilicate or sodalime.
 6. The display as recited in claim 1, whereinthe combined thickness of the first and second thickness is less than0.6 mm
 7. The display as recited in claim 1, wherein the combinedthickness of the first and second thickness is about 0.4 mm.
 8. Thedisplay as recited in claim 7, wherein the first thickness is about 0.25mm and the second thickness is about 0.15 mm
 9. The display as recitedin claim 1, wherein the first and second thickness are combined to forma combined thickness, and wherein the first thickness is larger thanhalf of the combined thickness, and the second thickness is smaller thanhalf of the combined thickness.
 10. The display as recited in claim 9,wherein the increase in the first thickness as compared to the thicknessof half of the combined thickness is same as the decrease in the secondthickness as compared to the thickness of half of the combinedthickness.
 11. The display as recited in claim 9, wherein the percentagechange of the increase or decrease as compared to a centerline valuecorresponding to half the combined thickness is between about 40% andabout 1%.
 12. The display as recited in claim 9, wherein the percentagechange of the increase or decrease as compared to a centerline valuecorresponding to half the combined thickness is between about 20-30%.13. The display as recited in claim 1, wherein said display furthercomprises: high density spacer elements placed between the first glasssheet and the second glass sheet, the high density spacer elements beingprovided every 6-10 pixels of said display.
 14. The display as recitedin claim 1, wherein said display is a liquid crystal display (LCD). 15.The display as recited in claim 1, wherein the first glass sheet and thesecond glass sheet are components of a liquid crystal module (LCM). 16.A method of forming a display with an asymmetric glass configuration,comprising: providing a first glass sheet having a first thickness;providing a second glass sheet having a second thickness; cutting thefirst glass sheet with a first cutting process, the first cuttingprocess forming a first edge on the first glass sheet; cutting thesecond glass sheet with a second cutting process that is different thanfirst cutting process, the second cutting process forming a second edgeon the second glass sheet; and positioning the first and second sheetsrelative to one another in order to form the display.
 17. The method asrecited in claim 16, wherein the first cutting process is a laser scribecutting process.
 18. The method as recited in claim 17, wherein thefirst thickness is configured as the lowest possible thickness capableof being laser scribed, and wherein the second thickness is configuredless than the lowest possible thickness capable of being laser scribed.19. The method as recited in claim 18, wherein the second cuttingprocess is a wheel scribing cutting process.
 20. The method as recitedin claim 16, wherein said providing the first and second glass sheetscomprise: selecting a combined thickness of the first thickness and thesecond thickness; forming the first glass sheet and the second glasssheet utilizing the combined thickness, said forming includingincreasing the first thickness for the first glass sheet whiledecreasing the second thickness for the second glass sheet.
 21. Themethod as recited in claim 20, wherein the increase is proportional tothe decrease.
 22. The method as recited in claim 16, wherein the secondthickness is not capable of being cut by the first process.